U.S. patent number 7,569,986 [Application Number 11/584,129] was granted by the patent office on 2009-08-04 for electron emission display having electron beams with reduced distortion.
This patent grant is currently assigned to Samsung SDI Co., Ltd.. Invention is credited to Cheol-Hyeon Chang, Eung-Joon Chi, Seung-Joon Yoo.
United States Patent |
7,569,986 |
Chi , et al. |
August 4, 2009 |
Electron emission display having electron beams with reduced
distortion
Abstract
An electron emission display includes first and second
substrates facing each other to form a vacuum envelope, a plurality
of driving electrodes formed on the first substrate, a plurality of
electron emission regions controlled by the driving electrodes, a
focusing electrode disposed on and insulated from the driving
electrodes and provided with first openings through which electron
beams pass, a plurality of phosphor layers formed on a surface of
the second substrate, an anode electrode formed on surfaces of the
phosphor layers, and a plurality of spacers for maintaining a gap
between the first and second substrates. The focusing electrode
includes second openings for forming a potential control unit for
forming a potential well, the potential control unit being formed
between the first openings to correspond to the spacers. The
potential well attracts the electron beams, improving the
directionality of the beams.
Inventors: |
Chi; Eung-Joon (Yongin-si,
KR), Yoo; Seung-Joon (Yongin-si, KR),
Chang; Cheol-Hyeon (Yongin-si, KR) |
Assignee: |
Samsung SDI Co., Ltd.
(Suwon-Si, KR)
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Family
ID: |
37769417 |
Appl.
No.: |
11/584,129 |
Filed: |
October 20, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070096626 A1 |
May 3, 2007 |
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Foreign Application Priority Data
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Oct 31, 2005 [KR] |
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10-2005-0103526 |
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Current U.S.
Class: |
313/497; 313/310;
313/495; 313/496; 315/169.3 |
Current CPC
Class: |
H01J
29/467 (20130101); H01J 29/481 (20130101); H01J
31/127 (20130101) |
Current International
Class: |
H01J
1/62 (20060101); H01J 63/04 (20060101) |
Field of
Search: |
;313/306,309-310,293-304,495-497 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 696 465 |
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Aug 2006 |
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EP |
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1 708 237 |
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Oct 2006 |
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EP |
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11-111157 |
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Apr 1999 |
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JP |
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WO 00/24027 |
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Apr 2000 |
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WO |
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WO 02/065499 |
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Aug 2002 |
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WO |
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Other References
European Search Report dated Apr. 5, 2007, for EP 06122729.4, in
the name of Samsung SDI Co., Ltd. cited by other.
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Primary Examiner: Roy; Sikha
Attorney, Agent or Firm: Christie, Parker & Hale,
LLP
Claims
What is claimed is:
1. An electron emission display comprising: a first substrate; a
second substrate facing the first substrate to form a vacuum
envelope; a plurality of driving electrodes formed on the first
substrate; a plurality of electron emission regions controlled by
the driving electrodes; a focusing electrode disposed on and
insulated from the driving electrodes and provided with a plurality
of first openings through which electron beams pass; a plurality of
phosphor layers formed on a surface of the second substrate; an
anode electrode formed on surfaces of the phosphor layers; and a
plurality of spacers for maintaining a gap between the first and
second substrates, wherein the focusing electrode comprises a
potential control unit for forming a potential well to compensate
for distortion of the electron beams caused when electric charges
are accumulated on the spacers, the potential control unit being
formed by removing a portion of the focusing electrode to expose a
top surface of an underlying insulation layer contacting the
focusing electrode, and positioned between at least two of the
first openings to correspond to the spacers such that the potential
control unit is configured to form an electric field for countering
an effect on the electron beams of an electric field from the
electric charges accumulated on the spacers.
2. An electron emission display comprising: a first substrate; a
second substrate facing the first substrate to form a vacuum
envelope; a plurality of driving electrodes formed on the first
substrate; a plurality of electron emission regions controlled by
the driving electrodes; a focusing electrode disposed on and
insulated from the driving electrodes and provided with a plurality
of first openings through which electron beams pass; a plurality of
phosphor layers formed on a surface of the second substrate; an
anode electrode formed on surfaces of the phosphor layers; and a
plurality of spacers for maintaining a gap between the first and
second substrates, wherein the focusing electrode comprises a
potential control unit for forming a potential well to compensate
for distortion of the electron beams caused when electric charges
are accumulated on the spacers, the potential control unit being
formed by removing a portion of the focusing electrode to expose an
underlying insulation layer, and positioned between at least two of
the first openings to correspond to the spacers such that the
potential control unit is configured to form an electric field for
countering an effect on the electron beams of an electric field
from the electric charges accumulated on the spacers, and wherein
the underlying insulation layer is formed under the focusing
electrode for insulating the focusing electrode from the driving
electrodes, wherein the potential control unit includes a plurality
of second openings formed on the focusing electrode to expose the
underlying insulation layer.
3. The electron emission display of claim 2, wherein the focusing
electrode is formed as a single body and the spacers are disposed
on the focusing electrode.
4. The electron emission display of claim 2, wherein the spacers
are wall-type spacers.
5. The electron emission display of claim 2, wherein the spacers
have a cylindrical shape.
6. The electron emission display of claim 2, wherein the potential
control unit is formed in a rectangular shape.
7. The electron emission display of claim 2, wherein the driving
electrodes include a plurality of cathode electrodes on which the
insulation layer is formed and a plurality of gate electrodes
formed on the cathode electrodes and crossing the cathode
electrodes, and wherein the electron emission regions are formed on
the cathode electrodes at respective crossed areas of the cathode
and gate electrodes.
8. The electron emission display of claim 7, wherein each of the
first openings are formed for each of the crossed areas of the
cathode and gate electrodes.
9. The electron emission display of claim 7, wherein the electron
emission regions are formed of a material selected from the group
consisting of carbon nanotubes, graphite, graphite nanofibers,
diamonds, diamond-like carbon, C.sub.60, silicon nanowires, and
combinations thereof.
10. The electron emission display of claim 2, wherein the potential
control unit is formed as a single second opening corresponding to
a length of a corresponding one of the spacers.
11. The electron emission display of claim 2, wherein the potential
control unit is formed with at least two sections along a length of
a corresponding one of the spacers.
12. The electron emission display of claim 11, wherein each of the
second openings of the potential control unit corresponds to each
of the first openings.
13. An electron emission display comprising: a first substrate; a
second substrate facing the first substrate; a driving electrode
formed on the first substrate; an electron emission region
electrically connected to the driving electrode; an insulation
layer formed on the driving electrode; a focusing electrode
contacting the insulation layer and provided with a first opening
through which an electron beam passes; and a spacer for maintaining
a gap between the first and second substrates, wherein the focusing
electrode comprises a potential control unit for forming a
potential well to compensate for distortion of the electron beam
caused when electric charges are accumulated on the spacer, the
potential control unit being formed by removing a portion of the
focusing electrode to expose a top surface of the insulation layer,
and configured to form an electric field for countering an effect
on the electron beam of an electric field from the electric charges
accumulated on the spacer.
14. The electron emission display of claim 13, wherein the
potential control unit is formed as a single second opening
corresponding to a length of the spacer.
15. The electron emission display of claim 13, wherein the
potential control unit is formed with at least two sections along a
length of a corresponding spacer.
16. An electron emission display comprising: a first substrate; a
second substrate facing the first substrate; a driving electrode
formed on the first substrate; an electron emission region
electrically connected to the driving electrode; an insulation
layer formed on the driving electrode; a focusing electrode
disposed on the insulation layer and provided with a first opening
through which an electron beam passes; and a spacer for maintaining
a gap between the first and second substrates, wherein the focusing
electrode comprises a potential control unit for forming a
potential well to compensate for distortion of the electron beam
caused when electric charges are accumulated on the spacer, the
potential control unit being formed by removing a portion of the
focusing electrode and configured to form an electric field for
countering an effect on the electron beam of an electric field from
the electric charges accumulated on the spacer; and wherein the
potential control unit includes a plurality of second openings
formed on the focusing electrode to expose the insulation
layer.
17. The electron emission display of claim 16, wherein the driving
electrode includes a cathode electrode on which the insulation
layer is formed and a gate electrode formed on the cathode
electrode and crossing the cathode electrode, and wherein the
electron emission region is formed on the cathode electrode at the
crossing area of the cathode and gate electrodes.
18. An electron emission display comprising: a first substrate; a
second substrate facing the first substrate; a driving electrode
formed on the first substrate; an electron emission region
controlled by the driving electrode; a focusing electrode insulated
from the driving electrode and provided with a plurality of first
openings through which electron beams pass; a phosphor layer formed
on a surface of the second substrate; an anode electrode formed on
a surface of the phosphor layer; and a spacer for maintaining a gap
between the first and second substrates, wherein the focusing
electrode comprises a potential control unit for forming a
potential well to compensate for distortion of the electron beams
caused when electric charges are accumulated on the spacer, the
potential control unit being formed by removing a portion of the
focusing electrode to expose a top surface of an underlying
insulating layer contacting the focusing electrode and positioned
between at least two of the first openings and corresponding to the
spacer such that the potential control unit is configured to form
an electric field for countering an effect on the electron beams of
an electric field from the electric charges accumulated on the
spacer.
Description
CROSSED-REFERENCE TO RELATED APPLICATION
This application claims priority to and the benefit of Korean
Patent Application No. 10-2005-0103526, filed on Oct. 31, 2005, in
the Korean Intellectual Property Office, the entire content of
which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron emission display, and
more particularly, to an electron emission display that can
effectively focus electron beams emitted from electron emission
regions by improving a focusing electrode.
2. Description of Related Art
In general, an electron emission element can be classified,
depending upon the kind of electron source, into a hot cathode type
or a cold cathode type.
There are several types of cold cathode electron emission elements,
including Field Emitter Array (FEA) elements, Surface Conduction
Emitter (SCE) elements, Metal-Insulator-Metal (MIM) elements, and
Metal-Insulator-Semiconductor (MIS) elements.
An FEA element includes electron emission regions and cathode and
gate electrodes that are used as the driving electrodes. The
electron emission regions are formed of a material having a
relatively low work function and/or a relatively large aspect
ratio, such as a molybdenum-based (Mo) material, a silicon-based
(Si) material, and a carbon-based material such as carbon nanotubes
(CNT), graphite, and diamond-like carbon (DLC) so that electrons
can be effectively emitted when an electric field is applied to the
electron emission regions under a vacuum atmosphere (or vacuum
state). When the electron emission regions are formed of the
molybdenum-base material or the silicon-based material, they are
formed as a pointed tip structure.
The electron emission elements are arrayed on a first substrate to
form an electron emission device. A light emission unit (having
phosphor layers and an anode electrode) is formed on a second
substrate. The first and second substrates, the electron emission
device, and the light emission unit establish an electron emission
display.
The electron emission device includes electron emission regions and
a plurality of driving electrodes functioning as scanning and data
electrodes. The electron emission regions and the driving
electrodes control the on/off operation of each pixel and the
amount of electrons emitted. The electrons emitted from the
electron emission regions excite the phosphor layers to display an
image (which may be predetermined).
The first and second substrates are sealed together at their
peripheries using a sealing member, and the inner space between the
first and second substrates is exhausted to form a vacuum envelope.
In addition, a plurality of spacers are disposed in the vacuum
envelope between the first and second substrates to prevent the
substrates from being damaged or broken by a pressure difference
between the inside and outside of the vacuum envelope.
The spacers are exposed to the internal space of the vacuum
envelope in which electrons emitted from the electron emission
regions move. The spacers are positively or negatively charged by
the electrons colliding therewith. The charged spacers may distort
the electron beam path by attracting or repulsing the electrons. As
a result, a non-emission region of the phosphor layer
increases.
For example, when the spacers are positively charged, the spacers
attract the electrons such that a relatively large amount of
electrons collides with a portion of the phosphor layer near the
spacers. As a result, the luminance of the portion of the phosphor
layer around the spacers is higher than the luminance of other
portions. In this case, the spacers may be detected (observed) on a
screen.
In order to reduce or prevent the distortion of the electron beam
path, the spacers may be coated with an insulation material or may
be connected to the electrodes to discharge the electric charges
accumulated on the spacers.
However, due to defective connections between the spacers and the
electrodes, the discharge of the electric charges is not
effectively realized.
SUMMARY OF THE INVENTION
An aspect of the present invention provides an electron emission
display that can compensate for the distortion (or scan distortion)
of electron beams, which is caused by the positive or negative
charge accumulated on the spacers, by varying an equipotential line
around the electron beams.
According to an exemplary embodiment of the present invention,
there is provided an electron emission display including: first and
second substrates facing each other to form a vacuum envelope; a
plurality of driving electrodes formed on the first substrate; a
plurality of electron emission regions controlled by the driving
electrodes; a focusing electrode disposed on and insulated from the
driving electrodes and provided with first openings through which
electron beams pass; a plurality of phosphor layers formed on a
surface of the second substrate; an anode electrode formed on
surfaces of the phosphor layers; and a plurality of spacers for
maintaining a gap between the first and second substrates, wherein
the focusing electrode comprises a potential control unit for
forming a potential well, the potential control unit being formed
between the first openings and corresponding to the spacers.
The potential control unit may be formed by removing a portion of
the focusing electrode.
The potential control unit may include second openings formed on
the focusing electrode to expose an insulation layer formed under
the focusing electrode.
The focusing electrode may be formed in a single layer with the
spacers disposed on the focusing electrode.
The spacers may be wall-type spacers.
The potential control unit may be formed in a single section
corresponding to a length of the spacer, or, alternatively, the
potential control unit may be divided into at least two sections
corresponding to a length of each spacer.
Each section of the potential control unit may correspond to each
first opening of the focusing electrode.
The spacer may be formed in a cylindrical shape.
The potential control unit may be formed in a rectangular
shape.
The driving electrodes may include a plurality of cathode
electrodes on which the insulation layer is formed and a plurality
of gate electrodes formed on the cathode electrodes and crossing
the cathode electrodes. The electron emission regions are formed on
the cathode electrodes at each crossed area of the cathode and gate
electrodes.
The first openings in the focusing electrode may correspond on a
one to one basis with each crossed area of the cathode and gate
electrodes.
The electron emission regions may be formed of a material selected
from the group consisting of carbon nanotubes, graphite, graphite
nanofibers, diamonds, diamond-like carbon, C.sub.60, silicon
nanowires, and combinations thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, together with the specification,
illustrate exemplary embodiments of the present invention, and,
together with the description, serve to explain the principles of
the present invention.
FIG. 1 is a partial exploded perspective view of an electron
emission display according an embodiment of the present
invention;
FIG. 2 is a partial sectional view of the electron emission display
of FIG. 1;
FIG. 3 is a partial top view of the electron emission display of
FIG. 1;
FIG. 4 is a partial top view of an electron emission display
according to another embodiment of the present invention; and
FIG. 5 is a partial top view of an electron emission display
according to another embodiment of the present invention.
DETAILED DESCRIPTION
In the following detailed description, only certain exemplary
embodiments of the present invention are shown and described, by
way of illustration. As those skilled in the art would recognize,
the invention may be embodied in many different forms and should
not be construed as being limited to the embodiments set forth
herein.
FIGS. 1 through 3 show an electron emission display 1 according to
an embodiment of the present invention.
Referring to FIGS. 1 and 2, the electron emission display 1
includes first and second substrates 2 and 4 facing each other and
spaced apart by a distance (which may be predetermined). A sealing
member (not shown) is provided at the peripheries of the first and
second substrates 2 and 4 to seal them together. The space defined
by the first and second substrates 2 and 4 and the sealing member
is exhausted to form a vacuum envelope (or chamber) kept to a
degree of vacuum of about 10.sup.-6 Torr.
A plurality of electron emission elements are arrayed on the first
substrate 2 to form an electron emission device 100. The electron
emission display 1 is composed of the electron emission device 100
and the second substrate 4 on which a light emission unit 200 is
formed.
A plurality of cathode electrodes (first driving electrodes) 6 are
arranged on the first substrate 2 in a stripe pattern extending
along a direction (a direction of a y-axis in FIG. 1) and a first
insulation layer 8 is formed on the first substrate 2 to cover the
cathode electrodes 6. A plurality of gate electrodes (second
driving electrodes) 10 are formed on the first insulation layer 8
in a stripe pattern extending along a direction (a direction of an
x-axis in FIG. 1) to cross the cathode electrodes 6 at right
angles.
Each crossed area of the cathode and gate electrodes 6 and 10
defines a unit pixel. One or more electron emission regions 12 are
formed on the cathode electrode 6 at each unit pixel. Openings 82
and 102 corresponding to the electron emission regions 12 are
formed on the first insulation layer 8 and the gate electrodes 10
to expose the electron emission regions 12.
The electron emission regions 12 may be formed of a material which
emits electrons when an electric field is applied thereto under a
vacuum atmosphere, such as a carbonaceous material and/or a
nanometer-sized material. For example, the electron emission
regions 12 may be formed of carbon nanotubes (CNT), graphite,
graphite nanofibers, diamonds, diamond-like carbon (DLC), C.sub.60,
silicon nanowires, or combinations thereof.
Alternatively, the electron emission regions 12 may be formed as a
Molybdenum-based and/or Silicon-based pointed-tip structure.
The electron emission regions 12 may be formed in series along a
length of one of the cathode and gate electrodes 6 and 10. Each of
the electron emission regions 12 may have a flat, circular top
surface. The arrangement and shape of the electron emission regions
12 are, however, not limited to the above description.
In the foregoing description, an embodiment where the gate
electrodes 10 are placed above the cathode electrodes 6 with the
first insulation layer 8 interposed therebetween is described, but
the present invention is not limited to this embodiment. That is,
the gate electrodes may be disposed under the cathode electrodes
with the first insulation layer interposed therebetween. In this
case, the electron emission regions may be formed on sidewalls of
the cathode electrodes on the first insulation layer.
A second insulation layer 16 is formed on the first insulation
layer 8 while covering the gate electrodes 10, and a focusing
electrode 14 is formed on the second insulation layer 16. The gate
electrodes 10 are insulated from the focusing electrode 14 by the
second insulation layer 16. Openings 142 and 162 through which
electron beams pass are formed through the second insulation layer
16 and the focusing electrode 14.
Each of the openings 142 of the focusing electrode 14 may be formed
for each unit pixel to focus the electrons emitted for each unit
pixel. Alternatively, each of the openings 142 of the focusing
electrodes 14 may be formed for each opening 102 of the gate
electrode 10 to individually focus the electrons emitted from each
electron emission region 12. The former is shown in this
embodiment.
In addition, the focusing electrode 14 may be formed on an entire
surface of the second insulation layer 16 or may be formed in a
certain (or predetermined) pattern having a plurality of
sections.
Describing the light emission unit 200, phosphor layers 18 such as
red, green and blue phosphor layers 18R, 18G and 18B are formed on
a surface of the second substrate 4 facing the first substrate 2.
Black layers 20 for enhancing the contrast of the screen are
arranged between the red, green and blue phosphor layers 18R, 18G
and 18B. The phosphor layers 18 may be formed to correspond to the
unit pixels defined on the first substrate 2.
An anode electrode 22 formed of a conductive material, such as
aluminum, is formed on the phosphor and black layers 18 and 20. The
anode electrode 22 functions to heighten the screen luminance by
receiving a high voltage required to accelerate the electron beams,
and by reflecting the visible rays radiated from the phosphor
layers 18 to the first substrate 2 back toward the second substrate
4.
Alternatively, the anode electrode 22 can be formed of a
transparent conductive material, such as Indium Tin Oxide (ITO),
instead of a metallic material. In this case, the anode electrode
22 is formed on the second substrate 4, and the phosphor and black
layers 18 and 20 are formed on the anode electrode 22.
Alternatively, the anode electrode 22 may include a transparent
conductive layer and a metallic layer.
Disposed between the first and second substrates 2 and 4 are
spacers 24 for uniformly maintaining a gap between the first and
second substrates 2 and 4. The spacers 24 are arranged
corresponding to the black layer 20 so that the spacers 24 do not
obstruct the phosphor layers 18. In FIG. 1, a wall-type spacer is
shown.
According to this embodiment, in order to provide directionality to
the electron beam, the focusing electrode 14 includes a potential
control unit for forming a potential well. As shown in FIG. 1, the
potential control unit is formed by eliminating a portion of the
focusing electrode 14. The potential control unit includes an
opening 144 formed through the focusing electrode 14 to expose the
second insulation layer 16. Hereinafter, for descriptive
convenience, the openings for allowing the electron beams to pass
will be referred to as first openings and the opening for the
potential control unit are referred to as second openings.
As shown in FIG. 2, the second opening 144 forms a potential well
E, which is concave with respect to the second substrate 4 so that
an equipotential line formed along the surface of the focusing
electrode 14 can have a potential lower than the surrounding
potential. The potential well E attracts the electron beam
traveling toward the second substrate 4. Therefore, the electron
beams that would be deflected toward the spacer 24 are attracted by
the potential well E, as a result of which the directionality of
the electron beams can be improved.
The second opening 144 may be formed between the first openings 142
to correspond to the spacer 24. In this case, a distortion of the
electron beam path (a state where the electron beam path is curved
in a direction indicated by solid arrow of FIG. 2), caused by the
spacer 24 that is positively charged by the secondary electron
emission, can be reduced or prevented. That is, the potential well
E is formed around the first opening 142 at a location facing the
spacer 24 so that the electron beam attractive force of the spacer
24 can be balanced with the electron beam attractive force of the
potential well E, thereby maintaining the directionality of the
electron beam (indicated by the dotted arrow of FIG. 2).
Referring to FIG. 3, the second opening 144 may be formed in a
rectangular single section so that the potential well is formed
along (or correspond to) the length of the wall-type spacer 24.
FIG. 4 shows an electron emission display according to another
embodiment of the present invention.
Referring to FIG. 4, second openings (or sections) 146 are formed
on a focusing electrode 14', which corresponds to one spacer 24'.
Each of the second openings (or sections) 146 corresponds to at
least one of the first opening 142'.
FIG. 5 shows an electron emission display according to another
embodiment of the present invention.
FIG. 5 shows a spacer 24'' formed in a cylindrical shape. A second
opening 148 corresponding to the cylindrical spacer 24'' is formed
on a focusing electrode 14'' between two of the first openings
142''.
In FIGS. 4 and 5, the reference numerals 12' and 12'' denote the
electron emission regions.
As described above, the arrangement, shape, position, and size of
the second opening can be varied according to the shape of the
spacer, the types of electric charge, the degree of the electron
beam distortion, and other suitable factors.
The above-described electron emission display is driven when a
certain (or predetermined) voltage is applied to the cathode, gate,
focusing, and anode electrodes 6, 10, 14, and 22.
For example, the cathode electrodes 6 may serve as scanning
electrodes receiving a scan drive voltage, and the gate electrodes
10 may function as data electrodes receiving a data drive voltage,
or vice versa. The focusing electrode 14 receives a voltage for
focusing the electron beams, for example, 0V or a negative direct
current voltage ranging from several to several tens of volts. The
anode electrode 22 receives a voltage for accelerating the electron
beams, for example, a positive direct current voltage ranging from
hundreds through thousands of volts.
Electric fields are formed around the electron emission regions 12
at unit pixels where a voltage difference between the cathode and
gate electrodes 6 and 10 is equal to or higher than a threshold
value and thus the electrons are emitted from the electron emission
regions 12. The emitted electrons are attracted to the
corresponding phosphor layers 18 by the high voltage applied to the
anode electrode 22, and strike the phosphor layers 18, thereby
exciting the phosphor layers 18 to emit light.
During the above-described driving operation, the spacer 24 may be
positively charged to attract the electron beam passing through the
first opening 142, 142', 142''. But because the potential well E is
formed by the second opening 144, 146, 148 at the opposite side of
the first opening 142, 142', 142'' to attract the electron beam,
the attractive force formed by the potential well compensates for
the attractive force of the spacer. As a result, the electron beams
can maintain their desired paths without being deflected.
Although the electron emission display in the above embodiments is
described as having the FEA type of electron emission elements, the
present invention is not limited to this example. That is, the
present invention may be applied to an electron emission display
having other types of electron emission elements such as SCE
elements, MIM elements and MIS elements.
According to the present invention, by providing the potential
control unit forming the potential well on the focusing electrode,
the electron beam distortion phenomenon caused by the spacer can be
reduced or prevented. Therefore, the non-emission area of the
phosphor layer can be reduced, thereby realizing a high quality
image.
While the invention has been described in connection with certain
exemplary embodiments, it will be appreciated by those skilled in
the art that the invention is not limited to the disclosed
embodiments, but, on the contrary, is intended to cover various
modifications included within the principles and spirit of the
invention, the scope of which is defined in the claims and their
equivalents.
* * * * *